1. Field of the Invention
The present invention relates to chemical disinfection and sanitizing and, more particularly, to an improved biocidal aldehyde composition for surface disinfection/sterilization.
2. Description of the Background
The purpose of disinfection is to reduce microbial contamination to an innocuous level. There is a widespread need for effective microbials in the healthcare industry (e.g., medical instrument sterilization). There are also myriad existing compositions that purport to solve the need, but in reality the results are mixed. Moreover, certain chemicals are inappropriate for certain situations. For example, Iodine is one of the most effective antimicrobial agents known. It is essentially bactericidal, and in diluted form the bacteriostatic and bactericidal action is practically identical. Iodine is active against a broad series of organisms including TB, pathogenic fungi, and viruses of both lipophilic and hydrophilic types. Although effective as an antiseptic wash and irrigant over a wide pH range it is best at an acid pH.
There are several combinations of quaternary ammonium compounds used for biocidal purposes, but they are application specific. Quaternary ammonium compounds are inhibitory to vegetative organisms and fungi but are not tuberculocidal or sporicidal. Quaternary ammonium compounds cannot generally be provided in concentrate form because they are inactivated by hard water (water with more than 400 ppm of carbonates). They also present an environmental problem. Certain dual quaternary ammonium compounds have improved biocidal activity, stronger detergency and a low level of toxicity, but they still have not solved the hard water problem that reduces or inhibits their activity, nor the environmental problems. For example, U.S. Pat. No. 4,983,635 issued Jan. 8, 1991, and U.S. Pat. No. 5,284,875 issued Feb. 8, 1994, solved the hard water problem and improved but did not effectively solve the biocidal activity. Moreover, due to the addition of phenolics this prior art increased the toxicity problem.
Glutaraldehyde is still currently the most important high level disinfectant/sterilant in health care usage. However, its use over the years has shown it to be erratic, failing in certain tuberculosis (TB) tests. Moreover, it requires burdensome time/temperature control (residence time of 45-90 minutes for disinfection, and controlled temperature of from 20 C to 25-30 C). Consequently, glutaraldehyde has very limited usage in clinical settings where temperatures are between 20-22 degrees C. If the user fails to warm the solution or its labels do not indicate that this warming should accompany its use, there is risk of ineffectiveness. The most popular commercial product Cidex™ requires activation and dating to make it useful. Thus, proper usage entails a three step procedure and meticulous record-keeping regarding date of activation.
A different aldehyde, orthophthaldehyde (OPA), has now come into use. Johnson and Johnson developed an original formulation in the late 1980s described in U.S. Pat. No. 4,851,449 and in subsequent continuation in part application(s). This OPA has been approved by the FDA as a high level disinfectant with a twelve minute disinfection time at 20-22 degrees C. Its sterilization time is listed between 24-32 hours. OPA interacts with amino acids and proteins of microorganisms. OPA is lipophilic which improves its uptake in the cell walls. Thus, OPA has been shown to be more penetrating than glutaraldehyde. The J&J OPA concentration is 0.55% by weight at a pH 3-9. It has been shown to be effective in a purely aqueous immersion solution. Metrex Research Corp. continues to sell a modified formulation referred to as OPA+, with an increased OPA concentration of 0.6% (0.05% more OPA), plus buffers, a corrosion inhibitor, and a chelating agent. In essence the formula is the same as the J&J product, with no faster kill time, but claims of 60% more treatment. However, if one looks at the mechanism by which OPA works it becomes biologically clear where the weaknesses lie. OPA is an aromatic dialdehyde. The severe test for cidal effectiveness are gram negative bacteria, mycobacteria and sporecoated organisms. OPA is not completely effective in clinical use at its concentration of 0.5% and pH 6.5. Failures occur and have been reported in literature surveys. The benzene ring of OPA is a planar, rigid structure. Therefore, OPA has no flexibility as a result of steric hinderance. In addition, OPA only reacts with primary amines. OPA is bactericidal at low concentrations to staphylococci and gram-bacteria. The poor sporicidal activity is due to low concentration and low pH. It has been noted that if the temperature is raised from the normal 20 degrees C. to 30 degrees it improves. However, this is impractical. Regarding mycobacteria, a similar problem is present. The lipophilic aromatic component of OPA does not reliably penetrate the lipid-rich cell wall of mycobacteria and gram (−) bacteria. Indeed, subsequent studies show that OPA exhibits selective bactericidal activity, good against P. aeruginosa, limited activity against mycobacterial strains. Shackelford et al., Use of a New Alginate Film Test To Study The Bactericidal Efficacy Of The High-Level Disinfectant Ortho-Phthalaldehyde, Journal of Antimicrobial Chemotherapy, 57(2):335-338 (2006).
What is needed is a simple one-step formulation for more effective disinfection/sterilization of health care instruments and other surfaces.